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Dynamically adding forms to a formset. OOP version.

Author:
halfnibble
Posted:
May 13, 2015
Language:
JavaScript
Version:
1.7
Tags:
django javascript jquery formset inlineformset
Score:
1 (after 1 ratings)

What It Is

This is a JavaScript-based solution to dynamically add and remove forms in formsets and inlineformsets. It requires jQuery.

Originally based on this Snippet: https://djangosnippets.org/snippets/1389/

I have done a lot of work to make it OO, and am using it in production on pages with multiple inlineformsets, and even nested inlineformsets (I call it, "Inlineformset Inception").

My hope is that the code and example are enough to show how it works.

Usage Details

In the example usage, I am using a CSS class, 'light', to make every other form have a light background color. My form placeholder is an element with an ID of 'formset-placeholder' (the default). And the form selector is a class name of 'dynamic-form' (the default).

When I have time, I will create a GitHub repository with the code and completed examples.

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JavaScript
==========

/* For dynamically adding/deleting Django inline formsets
 * Original snippet from: https://djangosnippets.org/snippets/1389/
 * Original snippet by: elo80ka
 * This version by: halfnibble (Josh Wedekind)
 * Updated 5/13/2015
 */

var Formset = (function() {
    var callbacks = {},
        empty_form = {},
        form_count = 0,
        form_manager = {},
        form_placeholder = $('#formset-placeholder')[0],
        form_selector = '.dynamic-form',
        prefix = 'formset';        

    function setup(context) {
        /***************************************
         * Common context attributes           *
         *   prefix:           'formset'       *
         *   form_selector:    '.dynamic-form' *
         *   form_placeholder: DOM.element     *
         *   callbacks:        { funcs... }    *
         ***************************************/
        $.extend(this, context);

        // Set a few more attributes
        this.form_manager = $('#id_' + this.prefix + '-TOTAL_FORMS');
        this.form_count = parseInt(this.form_manager.val());        
        if (this.form_placeholder === undefined || this.form_placeholder === [])
            this.form_placeholder = $('#' + this.prefix + '-placeholder');

        // Setup the empty form for add_form()
        var empty_form = $(this.form_selector + ':first').clone(true).get(0);
        // Clear all values except for hidden field values.
        $(empty_form).find(':input')
            .removeAttr('checked')
            .removeAttr('selected')
            .not(':button, :submit, :reset, [type="hidden"], :radio, :checkbox')
            .val('')
            .attr('value',''); // Handle UpdateView default values
        this.empty_form = empty_form;

        if (this.callbacks.setup)
            this.callbacks.setup(this);
    }

    function add_form() {
        var self = this;

        // Assume new forms get last index counter
        var index = this.form_count;

        // Create form to add
        var form = $(this.empty_form).clone(true).get(0);
        this.update_index(form, index, false);
        
        // Add form after last one, or after the placeholder if none exist.
        if ($(this.form_selector + ':last').length > 0)
            $(form).insertAfter(
                $(this.form_selector + ':last')
            );
        else
            $(form).insertAfter(this.form_placeholder);

        // Update all pertinent form field indexes
        $(form).children('.hidden').removeClass('hidden');
        $(form).find('div, input, select, label, button').each( function() {
            self.update_index(this, index, false);
        });

        // Update index counter
        ++this.form_count;
        this.form_manager.val(this.form_count);

        if (this.callbacks.add_form)
            this.callbacks.add_form(this, form, index);

        return false;
    }

    function delete_form(button) {
        var self = this;
        $(button).parents(this.form_selector).hide(400, function() {
            var form = this;
            $(form).remove();
            --self.form_count;
            self.form_manager.val(self.form_count);

            // Delete anything else before updating
            if (self.callbacks.delete_form)
                self.callbacks.delete_form(self, form);

            // Update all formset indexes, etc.
            self.update_all();
        });

        return false;
    }

    function update_all() {
        var self = this;
        // Get list of all forms in formset
        var forms = $(this.form_selector);

        for (var index = 0; index < this.form_count; index++) {
            /*jshint loopfunc: true */
            var form = forms.get(index);

            // Update form index, then all pertinent field indexes
            this.update_index(form, index);
            $(form).find('div, input, select, label, button')
                .each( function() { self.update_index(this, index); });

            if (this.callbacks.update_all)
                this.callbacks.update_all(this, form, index);
        }
    }

    function update_index(element, index, external_links) { 
        if (external_links === undefined)
            external_links = true; // Default: update links to element ID
        var regex = new RegExp('(' + this.prefix + '-\\d+)');
        var replacement = this.prefix + '-' + index;

        if ($(element).attr("for"))
            $(element).attr(
                "for",
                $(element).attr("for")
                .replace(regex, replacement)
            );
        if (element.id) {
            // Update targets to element
            if (external_links === true)
                $('a[href="#'+element.id+'"]').attr('href', function (i, attr) {
                    return attr.replace(regex, replacement);
                });
            element.id = element.id.replace(regex, replacement);
        }
        if (element.name)
            element.name = element.name.replace(regex, replacement);
        if (element.getAttribute('data-prefix'))
            element.setAttribute(
                'data-prefix',
                element.getAttribute('data-prefix')
                .replace(regex, replacement)
            );

        // Use if you want to replace more field attributes
        // E.g. element.className
        if (this.callbacks.update_index)
            this.callbacks.update_index(this, element, index,
                                        regex, replacement);
    }

    return {
        // Properties
        callbacks: callbacks,
        empty_form: empty_form,
        form_count: form_count,
        form_manager: form_manager,
        form_placeholder: form_placeholder,
        form_selector: form_selector,
        prefix: prefix,
        // Methods
        setup: setup,
        add_form: add_form,
        delete_form: delete_form,
        update_all: update_all,
        update_index: update_index
    };
});



Example Usage
=============

(Placed below formset in template)

<script type="text/javascript">
    <!--
    var callbacks = {
        'setup': function(formset) {
            $(formset.form_selector).find('.delete-form-row').click( function(e) {
                e.preventDefault();
                formset.delete_form(this);
            });
            $('.add-form-row').click( function(e) {
                e.preventDefault();
                formset.add_form();
            });
        }, 

        'add_form': function(formset, form, index) {
            $(form).find('.delete-form-row').click( function(e) {
                e.preventDefault();
                formset.delete_form(this);
            });
            if (index % 2 !== 0)
                $(form).removeClass('light');
        },

        'update_all': function(formset, form, index) {
            if (index % 2 === 0)
                $(form).addClass('light');
            else
                $(form).removeClass('light');
        }
    };

    var formset = new Formset();

    formset.setup({
        prefix: '{{ formset.prefix }}',
        callbacks: callbacks
    });
    //-->
</script>

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